The present invention relates to electronics assemblies, and is primarily concerned with thermal management therein. Many such assemblies will be located in racks for housing in for example nineteen inch cabinets, or other size cabinets, in cabinets such as twenty three inch or metric cabinets. The assemblies may for instance be employed as servers for a number of systems, for example in local area networks (LANs), wide area networks (WANs), telecommunications systems or other operations such as database management or as internet servers.
Such an assembly will typically comprise a supporting chassis that houses a motherboard or backplane and a number of daughterboards or module cards that extend in planes generally perpendicular to the plane of the motherboard. Because of the amount of heat that is generated during operation of the equipment and the thermal sensitivity of the equipment, it is necessary to provide cooling fans in order to direct a current of air through the assembly or otherwise permanent damage would occur. In the case of large computer systems, this may be accomplished by arranging the fans in an array that extends over the cross-sectional area of the system. In order to simplify the assembly of the system the fans may be arranged in a tray which can be installed or replaced as a unit when one or more components of the tray fails.
Increasing package density in large computer systems brings additional challenges. Compactness is desirable in order to permit installation of more systems in limited space that is available in data centres where the equipment will be housed. However, increased component count in large systems, can cause an increase in downtime of the system where one of the components has failed. It is therefore desirable for such failure not to require shutdown of the system where possible, and if shutdown is necessary, to minimise the time taken.